Electropolishing apparatus



S P 2 1943- F. E. DRUMMOND ET AL 2,330,562

ELECTROPOLISHING' APPARATUS Filed Dec. 20, 1940 mMEw F Lson E.DRl/MMOND. B'DAVID E.BENCH,

Patented Sept. 28, 1943 ELECTROPOLISHING APPARATUS Folsom E. Drummondand David E. Bench, Dayton, Ohio, assignors to The Himmel BrothersCompany, Hamden, Conn, a corporation of Connecticut Application December20, 1940, Serial No. 370,972

3 Claims.

This invention relates to improvements in the method and apparatus formanufacturing structural members, and more particularly mouldingsconventionally used for ornamental purposes, such as for trimmings onautomobiles, refrigerators, stoves, etc. and on buildings as mouldingsand store fronts to support and hold plate glass windows and the like.

These mouldings consist of a two-ply metal member wherein the outer plyor covering surface is made of stainless steel, the inner or backingmember being formed of ordinary iron or steel.

It is an object of this invention to provide an improved method offabricating and finishing structural members of the character described.

Another object of this invention is to provide an improved method forpolishing stainless steel strip prior to uniting it with the core orbacking member to produce a finished structural moulding wherein theouter shell of stainless steel is highly polished.

Another object is to provide a combined electrolytic polishing andforming apparatus for manufacturing two ply structural members wherebythe outer ply comprises a highly polished thin metal strip which hasbeen electropolished and then formed over the backing member bysimultaneously shaping the polished strip in contact with the backing orcore member with roller dies to shape the inner core and outer polishedshell member to form a unitary structural article.

Another object is to provide an improved electropolishing unit fortreating metal strip material wherein one side of the strip is directlycontacted at numerous spaced points over the surface by electricalconductors whereby theelectric currentis uniformly distributed over theentire area of the'strip as it is moved along through the electrolyte.

These and other objects and advantages will be apparent from thefollowing description taken in connection with the drawing, whereinFigure 1 illustrates one embodiment of this invention showing anapparatus in section for electropolishing and fabricating a structuralmoulding member;

Figure 2 is an enlarged fragmentary portion in section of theelectropolishing anode and cathode arrangement between which the stripis drawn-during electropolishing of the strip;

Figure 3 is 'a fragmentary sectional view taken substantially on theline 3-3 of Figure 1;

Figure 4 is a sectional view through the fin ished moulding taken on theline 4-4 of Figure 1 and looking in the direction of the arrows.

In the forming and polishing of stainless steel strip it has been founddiiiicult to mechanically polish the stainless steel because of its verylow heat conductivity. By reason of this property,-

when stainless steel is polished the heat developed is not readilydissipated and unless the polishing is done very carefully the materialwill be overheated at places causing discoloration, buckling, ordeforming of the strip. This difiiculty has been overcome somewhat byproviding the stainless steel strip with a backing member of relativelyhigh heat conductivity so that the heat developed during the polishingoperation is conducted away fast enough to prevent scorching oroverheating of the strip. The backing strip also forms a, support forthe very thin stainless steel covering and provides a strong structuralmember.

By the improved method of making moulding strips and the like accordingto this invention, no difliculty is involved due to overheating of thestainless steel strip during polishing since the strip iselectropolished and fabricated to form a structural member.

Further, it has been the practice to form structuralv two-ply mouldingarticles by taking two strips of metal and simultaneously rolling orpressing them to the desired shape in contact with each other andpolishing the preformed structural member by the use of burnishing orpolishing wheels. By the improved method of this invention, thispreforming of the structural member and then polishing the article isavoided with its problems of handling the finished article. To this end,the material is handled and treated while it is in a strip or band formand can be readily drawn'from a reel and passed over guide rolls intoand out of a tank and the forming or shaping of the article into thefinal product is done after the polishing of the surface strip has beenperformed.

Referring to the drawing in detail, in Figure l a thin strip ofstainless steel, designated I 0, is withdrawn from a reel l I and passedinto the electropolishing unit, generally designated l2. This unitpreferably comprises an electropolish- .ing compartment l4, and rinsingchamber IS. The compartment I4 is suitably lined with a material such asrubber, glass, or lead which is resistant to attack by the electrolyteIS. The stainless steel strip Ill is retained under tension by the brakemeans t8 and is guided through the electropolishing and rinsingcompartments by the rolls 20. In the electropolishing compartment M thestrip, which acts as the anode, is passed beneath the cathode member 22while beme electrically connected to the positive electrode bar member26 by means of the conductive brush bristle contact members 25.

The strip is maintained flat and uniformly spaced from the cathode 22 bymeans of the insulating rod members 28 which are spaced 'at intervalslongitudinally of the strip beneath the cathode 22. The strip in thismanner is made the anode and the electric current is uniformlydistributed over the underside area of the strip and the cathode membercomprises a sheet which is maintained in close proximity to the surface30 of the strip so as to efiect an efllcient electropolishing of thesame as the strip is moved along. The insulating rod members 28 maybemade of glass, hard rubber, synthetic resin or other electricalinsulating material and preferably are of a thickness or diameter toenter the space between the cathode and the strip.

Where desired, suitable means may be provided for maintaining theelectrolyte at a temperature which is required for effecting theelectropolishing treatment.

Copper or lead may be used as the cathode material and the positivelycharged members 23 and 26 may be made of stainless steel or othersuitable alloy metal which does not become passive in the electrolyte.Copper or brass may also be used for forming the bar 24 and bristlemembers 28 used for contacting the strip.

The electrolyte bath composition does not form a part of this inventionand may consist of any one of the conventionally used electrolyticsolutions which have been employed for this purpose.

After the electropolishing treatment of the strip II), it is passed intothe rinsing compartmeat 15 which contains water or other appropriatesubstances and thence from the rinsing tank through a drier 33 and thenover the guide roll 35 where it is brought in contact with the backingstrip 38. The strip 38 preferably is of milder steel and forms a coremember supporting the stainless steel strip I which is of comparativelysmall gauge thickness. The two-ply strip material is then passed throughthe set of roller dies 40 and the material pressed into the desiredshape of moulding and the outer shell of stainless steel is locked orclinched onto the surface of the backing strip. After this operation,the moulding is passed between the bufiing wheels 42 to remove anyscratches or blemishes caused by the roller dies to provide a finishedmoulding wherein the surface has a bright and mirro-like finish.

Where the roller dies are made of such material so that the surface ofthe moulding is not marred, the buffing wheels 42 may be omitted.

The backing strip 38 may be of any suitable gauge and is simultaneouslyunwound from the coil 45. The proper tension is maintained by the brakemember 41, similarly as in unwinding the '5' estates conductivity sincethe grinding and polishing steps have been eliminated and the backingstrip is only required to form a support for the more expensive thinshell-like stainless steel covering which forms the ornamental moulding.Ordinarily, however, the supporting strip for the highly polished outersurface ply will be of metal which can be cold worked into the desiredshape of moulding. Where it is desired to have a moulding of very lightweight, the backing or supporting strip may be made of aluminum ormagnesium alloy steel which is very light and has a high tensilestrength.

The finished moulding may have a cross sectional shape, such asindicated in Figure 4, wherein the moulding comprises an outer covermember 50 formed of the core 52. The inner edges of the outer coverportion 60 are clinched over the edges of the inner core member, asshown at 58, in order firmly to lock the two members togather forming aunitary structural member.

The electropolishing treatment, as diagrammatically illustrated inFigure 1, is similar to electroplating except that the flow of currentis in reverse direction.

Where the cover strip which is to be electropolished is of suflicientthickness so that it can be readily supported on the bristle frictioncontact members 26 as it is passed along over the anode member 24, theinsulating spacer rods 28 between the cathode 22 and the strip may beomitted. Preferably, the spacer rod disk-like wheel members 54 areshaped as indicated in Figure 3.

These spaced disk-like wheel members 54 provide point contact with thestrip and cathode member whereby the strip is maintained at'a uniformdistance from the cathode without interfering with the passage ofelectric current from the surface of the strip to the cathode. In thisway, the highest efliciency of electropolishing can be effected over theentire surface area of the strip.

Solid rods in some instances may be substituted for the multipledisk-like construction of the members 28 where the current density andspeed of the strip is such that proper polishing can be eifected withoutinterference from the interposed rod members. It will also be understoodthat the spacer guide members 28 are suitably rotatably supported on theelectroplating unit in order properly to guide the strip therealongbetween the anode and cathode.

In electropolishlng, high current densities may be used and electrolytesconsisting of phosphoric acid, sulphuric acid, or mixtures of these withvarious additions of organic acids. Copper cathodes are preferably usedwhere high current carrying capacity is required. The distance betweenthe anode and the cathode must be carefully controlled and may beapproximately onequarter to three inches or more depending upon theelectrolyte, current density and particular strip material to bepolished. When polishing strip material of varied shape, the cathodeshould be shaped to conform with the strip being treated so that thesurface will coincide with that of the anode.

Some electrolyte baths may be efficiently operated at room temperature,while others should be maintained at a higher temperature, on the orderof to 250 degrees F. Steam coils or other suitable means may beinstalled in the electrolyte tank compartment for raising thetemperature of the bath when this is desired.

This invention is adapted for processing various types of structuralmembers wherein a polished bright surface is to be provided by a surfaceshell-like covering. However, this invention may also be utilized intreating various types of strip material which are to be polished andfabricated into an article. Ordinary heavy scale is removed by apickling treatment prior to electropolishing. This process may also beutilized in treating wire, band, sheet and spun shapes or castings andthe like. Further, the apparatus and method herein described may beemployed for electropolishing various types of metals other thanstainless steels, such as copper, brass, nickel, Monel, cobalt, zinc,tin, lead, aluminum, iron and their alloys.

. It will be further understood that this invention is not limited tothe particular details of the apparatus and method as described and thatvarious modifications may be made by those skilled'in the art withoutdeparting from the spirit and scope of this invention.

Having thus fully described our invention, what we claim as new anddesire to secure by Letters Patent is:

1. In an electrolytic polishing and forming ap paratus for manufacturinga composite strip having a backing strip and a thin shell-like coveringstrip of electropolished metal of the class consisting of stainlesssteels, copper, brass, nickel, Monel, cobalt, zinc, tin, lead, aluminum,iron and the alloys of said metals in a continuous process, comprisingthe means for feeding a thin, shelllike covering strip through anelectropolishing bath, means for supporting said shell-like coveringstrip comprising a plurality of electrically conductive brush bristlefriction contact members, which members are located closely adjacent toeach other as it is passed through said electropolishing path, saidcontact members forming a continuous support therefor and preventingbending or bowing of said strip during the electropolishing step.

2. In an electrolytic polishing and forming apparatus for manufacturinga composite strip having a backing strip and a thin shell-like coveringstrip of electropolished metal of the class consisting of stainlesssteels, copper, brass, nickel,

Monel, cobalt, zinc, tin, lead, aluminum, iron and the alloys of saidmetals in a continuous process, comprising means for feeding a thinshelllike covering strip through an electropolishing bath, means forsupporting said shell-like coverin strip comprising a plurality ofelectrically conductive brush bristle friction contact members, whichmembers are located closely adjacent to each other, as it is passedthrough said electropolishing path to form a continuous supporttherefor, and to prevent bending or bowing of said strip during theelectropolishing step.

3. In an electrolytic polishing and forming apparatus for themanufacture of a composite strip having a backing strip and a thinshell-like covering strip of electropolished metal of the classconsisting of stainless steels, copper, brass, nickel, Monel, cobalt,zinc, tin, lead, aluminum, iron, and the alloys of said metals in acontinuous process comprising an electropolishing bath, spaced rollers,means for supporting said shelllike covering strip comprising aplurality of electrically conductive brush bristles friction contactmembers located between said rollers to support said strip as it ispassed through said electropolishing path within said bath, saidelectrical friction contact members being located closely adjacent toeach other and acting to prevent bending or bowing of said strip duringthe electropolishing step.

FOLSOM E. DRUMMOND.

DAVID E. BENCH.

